Contest1388/U.cpp

#include <bits/stdc++.h>

using namespace std;

int main() {
    double x1, y1, x2, y2;
    cin >> x1 >> y1 >> x2 >> y2;
    cout << fixed << setprecision(3) << hypot(x1 - x2, y1 - y2);
    return 0;
}